Research On Thermal-structural-Optical Integrated Of Aspheric Window

With appropriate aspheric windows,the flight speed of the aircraft can be improved effectively,and the aircraft has the advantages of short completion time,long flight distance and so on.The conformal window studied in this paper is a kind of aspheric window.When the aircraft is flying at supersonic speed,the aspheric window will bear the aerodynamic pressure load and the aerodynamic thermal load,which causes the change of the window structure,leads to the poor imaging quality of the window,and affects the normal work of the aircraft.At present,for the problem of supersonic aspheric window,the thermal coupling analysis of the optical machine under the joint action of aerodynamic pressure load and aerodynamic thermal load has not been accomplished by researchers.To solve this problem,aiming at conformal windows,4 parts of research work are carried out.1 The computational fluid dynamics simulation of a conformal supersonic vehicle with a diameter of 203 mm and a length diameter ratio of 1:1 at a velocity of 2 Ma,2.5 Ma,3 Ma and an angle of attack of 0,10 and 20 degrees is completed.The model of the same size is set up to carry out the wind tunnel test of different groups of aerodynamic pressure loads corresponding to the simulation speeds and angles of attack.The comparison between numerical simulation and wind tunnel test shows that the accuracy of the simulation is over 95%,which verifies the accuracy of the simulation results.2 In order to verify the accuracy of aerodynamic thermal load analysis of computational fluid dynamics,a group of conformal aircraft wind tunnel thermal tests have been completed,and the simulation numerical comparison under the same environment parameters is carried out by using Fluent commercial software.The results show that the error between the simulation temperature and the theoretical value is only-0.37%.Numerical simulation can provide technical reference for wind tunnel thermal test,reduce blindness in wind tunnel test,and verify the accuracy of CFD numerical simulation.3 Based on the basic theory of thermodynamics and structural mechanics,the theoretical equation of finite element analysis of thermal fluid solid coupling is derived.By means of aerodynamic load numerical transfer method,the aerodynamic load obtained by fluid dynamics simulation is transferred to the coupled field,and the joint simulation platform is established.The simulation process of the thermal fluid solid coupling of the conformal window is realized,and the stress distribution and the surface node displacement of the aspheric window under the joint action of pneumatic pressure load and aerodynamic thermal load are obtained.The results show that the stress at the edge of the aspheric window is the largest and the displacement of the node changes the largest,and the maximum stress value meets the strength limit requirement.4 In order to evaluate the image quality after the change of the surface type of aspheric window,a new method of parametric design reconstruction is proposed by using the series expansion and the least square method in the curve fitting.A new method of parameterized surface reconstruction is proposed,and the shape of the test sample is reconstructed,and the transfer function values and the dot map before and after reconstruction are compared.The accuracy of the method is verified to meet the requirements of optical design.This method is used to reconstruct the surface profile of the aspheric window,and the image quality of the aspheric window is analyzed.The results show that the transfer function value is less than that of undeformed,and the cut-off frequency appears,and the RMS radius is obviously increased,and the difference exists in the system.The aerodynamic thermal load and aerodynamic pressure load have great influence on the imaging quality of aspheric windows.The aberration correction system can be used to optimize the imaging quality of aspheric windows.The innovation points of this article are as follows:(1)aiming at the problem of supersonic aspheric window,the thermo mechanical coupling analysis of aero pressure load and aerodynamic heating load is completed.(2)put forward a new method of parameterized surface reconstruction and reconstruct the shape of the aspheric window after the deformation.(3)A group of aspheric aircraft with a speed of 2.5 Ma and an angle of attack of 20 degrees were completed.Comparison test results and simulation results.Numerical simulation can provide reference for wind tunnel test and provide technical support for wind tunnel thermal test work.